In tool spray acoustic tuning layer

ABSTRACT

A method of making a sound insulating layered composite structure contacting a padding layer having a preformed shaped with a curable liquid composition to form an uncured or partially cured cap layer disposed over at least a portion of the padding layer. An uncured or partially cured cap layer is then cured to form the sound insulating composite structure of the present embodiment. An automobile sound insulating component is made from the method.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to methods of forming sound absorbingcomposite structures have an acoustic tuning layer.

2. Background Art

There is an increasing demand for the reduction of sound levels toimprove perception in the passenger compartments of automobiles.Development of methods and systems that accomplish such reductionsrequire an understanding of the potential internal and external noisesources in an automobile as well as the effect of various automobilecomponents in masking or attenuating such noise. Moreover, reduction ofnoise in the 1 KHZ to 5 KHz frequency range is particularly desirabledue to the increased sensitivity of vehicle passengers in that range forspeech intelligibility and speech clarity.

Some sound insulating components such as dash insulators and vehiclepassenger floor components act as acoustic tuning layers by controllingthe air permeability of a single layer within a composite. Examples ofsuch acoustic tuning layers include perforated films or fabrics thatresist air flow. In other variations, the layer may be coated with amaterial such as a sintered or powder coated thermoplastic. These layersshift the sound absorption of a composite to lower frequencies than itwould have if impermeable to air. A problem sound absorbing componenthaving such layers is that after the component is formed into a shapethe air permeability of the acoustic tuning layer is altered.

Accordingly, there is a need in the prior art for improved methods offorming sound insulating automobile components with adjustable airpermeability.

SUMMARY OF THE INVENTION

The present invention solves one or more problems of the prior art byproviding in at least one embodiment a method of making a soundinsulating layered composite structure. In the method of the invention,a sound insulating layered composite structure is formed from a paddinglayer. The padding layer has a preformed shaped corresponding to theautomobile component which is ultimately formed. The padding layer iscontacted with a curable liquid composition to form an uncured orpartially cured cap layer disposed over at least a portion of thepadding layer. Uncured or partially cured cap layer is cured to form thesound insulating composite structure of the present embodiment.Advantageously, the sound insulating layered composite structure of thepresent embodiment is useful for making a variety of sound insulatingautomotive components such as dash insulators.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart showing in cross section an embodiment of thepresent invention;

FIG. 2 is a flowchart showing in cross section an embodiment of thepresent invention in which the cap layer is first sprayed on a tool; and

FIGS. 3A and 3B provide a flowchart showing in cross section anembodiment of the present invention in which an insert is used forsupport.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Reference will now be made in detail to presently preferred compositionsor embodiments and methods of the invention, which constitute the bestmodes of practicing the invention presently known to the inventors.

In an embodiment of the present invention, a method of making a soundinsulating layered composite structure is provided. With reference toFIG. 1, the method of the present embodiment in cross section isillustrated. In the method of the invention, sound insulating layeredcomposite structure 10 is formed from padding layer 12. Padding layer 12has a preformed shaped corresponding the the automobile component whichis ultimately formed. Padding layer 12 is contacted with curable liquidcomposition 14 to form uncured or partially cured cap layer 16 which isdisposed over at least a portion of padding layer 12. Uncured orpartially cured cap layer 16 is cured to form sound insulating compositestructure 10 which includes cap layer 18 disposed over padding layer 12.Advantageously, cap layer 18 functions as an acoustic tuning layer.Sound insulating layered composite structure 10 thus formed has apredetermined air flow resistance. In a variation of the presentembodiment, padding layer 12 is contacted with curable liquidcomposition 14 to form uncured or partially cured cap layer 16 byspraying curable liquid composition 14 onto padding layer 12.

The method of the present invention advantageously allows for atailoring of the air flow resistance of the formed sound insulatingcomposite structure. In a variation of the present embodiment, the airflow resistance is determined as in ASTM C522-03. The entire disclosureof ASTM C522-03 is hereby incorporated by reference. Typically, the airflow resistance set by the method of the present embodiment is fromabout 300 to about 6000 rayl. Sound insulating layered composite 10 isalso characterized by the position of its peak sound absorption. In onevariation of the present embodiment, sound insulating layered compositestructure 10 has a peak sound absorption at a sound frequency from about500 and 6,400 Hz. In another variation of the present embodiment, soundinsulating layered composite structure has a peak sound absorption at asound frequency from about 1500 and 5000 Hz.

With reference to FIG. 2, another variation using spraying isillustrated. In this variation, curable liquid composition 14 is sprayedonto tool 20 to form uncured or partially cured cap layer 16. Uncured orpartially cured cap layer 16 is then transferred onto padding layer 12.After curing, sound insulating layered composite structure 10 is removedfrom tool 20.

With reference to FIGS. 3A and 3B, another variation of the presentinvention in which curable liquid 14 is sprayed is provided. In thisvariation, curable liquid composition 14 is sprayed onto insert 30 toform the uncured or partially cured cap layer 16 disposed over insert30. Insert 30 provides structural support to padding layer 12 which canbe non-rigid. Insert 30 is then positioned in mold 32. Next, paddinglayer 12 is also positioned in mold 32 proximate to uncured or partiallycured cap layer 14 which disposed over the insert to form soundinsulating assembly 34. Sound insulating assembly 34 is subsequentlycured and then removed from mold 32. Insert 30 is then removed fromsound insulating assembly 34 to form sound insulating layered compositestructure 10.

The curable liquid compositions used in the present invention may bethermally and/or photochemically cured. Uncured or partially cured caplayer 16 is substantially fully cured by heating. In one variation, thecurable liquid composition comprises a latex or polyurethane. Examplesinclude acrylic latex, ethylene vinyl acetate latex, and styrenebutadiene rubber latex. In another variation, the curable liquidcomposition comprises cross-linkable polymer precursors. In general,polymer precursors are cross-linking agents, oligomers, and monomers.Suitable polymer precursors for the methods of the invention include thecurable liquid composition comprises latex precursors or polyurethaneprecursors. Specific examples include, but are not limited to, acryliclatex precursors, ethylene vinyl acetate latex precursors, styrenebutadiene rubber latex precursors, and the like. In a further refinementof the invention, the curable comprises a two component system that ismixed prior to or during the step in which liquid composition 14 iscontacted with padding layer 12. Accordingly, cap layer 18 includes thepolymer residues of the polymer precursors. Typically, cap layer 18 hasa thickness from about 0.3 mil to about 0.25 mm. In another variation,cap layer 14 has a thickness from about 2 mil to about 10 mil.

Padding layer 14 is made from any of the materials typically used forsound insulating automotive components. In a variation, padding layer 14comprises a component selected from the group consisting of fibrouspadding and open cell foams. Such fibrous padding includes padding thatcomprises cotton (e.g., cotton shoddy) or polyester (e.g., polyethyleneterephthalate) or polyolefin (e.g., polypropylene) fibers. Padding layer14 optionally further comprises an additive selected from the groupconsisting of glass fibers, fire retardants, and combinations thereof.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

1. A method of making a sound insulating layered composite structurehaving a cap layer disposed over a padding layer, the method comprising:a) providing a padding layer, the padding layer having a preformedshaped; b) contacting a curable liquid composition with the paddinglayer to form an uncured or partially cured cap layer disposed over atleast a portion of the padding layer; and c) curing the uncured cap orpartially cured cap layer to form the sound insulating layered compositestructure such that the sound insulating layered composite structure hasa predetermined air flow resistance.
 2. The method of claim 1 whereinthe sound insulating layered composite has a peak sound absorption at asound frequency from about 500 and 6,400 Hz.
 3. The method of claim 1wherein the sound insulating layered composite has a peak soundabsorption at a sound frequency from about 1500 and 5000 Hz.
 4. Themethod of claim 1 wherein step b) comprises spraying the curable liquidcomposition onto the padding layer.
 5. The method of claim 1 whereinstep b) comprises spraying the curable liquid composition onto a tool toform the uncured or partially cured cap layer; and transferring theuncured or partially cured cap layer onto the padding layer.
 6. Themethod of claim 1 wherein step b) comprises: spraying the curable liquidcomposition onto an insert to form the uncured or partially cured caplayer disposed over the insert, the insert providing support to thepadding layer; positioning the insert in a mold; positioning the paddinglayer in the mold proximate to the uncured or partially cured cap layerdisposed over the insert to form a sound insulating assembly; curing thesound insulating assembly; removing the sound insulating assembly fromthe mold; removing the insert from the assembly to form the soundinsulating layered composite.
 7. The method of claim 1 wherein the airflow resitance is from about 300 to about 6000 rayl.
 8. The method ofclaim 1 wherein the curable liquid composition comprises across-linkable polymer.
 9. The method of claim 1 wherein the curableliquid composition comprises a latex or polyurethane.
 10. The method ofclaim 9 wherein the curable liquid composition comprises an acryliclatex, an ethylene vinyl acetate latex, a styrene butadiene rubberlatex.
 11. The method of claim 1 wherein the curable liquid compositioncomprises a two component system that is mixed prior to or during stepb).
 12. The method of claim 1 wherein the uncured or partially cured caplayer is substantially fully cured by heating.
 13. The method of claim 1wherein the cap layer has a thickness from about 0.3 mil to about 0.25mm.
 14. The method of claim 1 wherein the cap layer has a thickness fromabout 2 mil to about 10 mil.
 15. The method of claim 1 wherein thepadding layer comprises a component selected from the group consistingof fibrous padding and open cell foams.
 16. A method of making a soundinsulating layered composite structure having a cap layer disposed overa padding layer, the method comprising: a) providing a padding layer,the padding layer having a preformed shaped; b) spraying a curableliquid composition onto an insert to form an uncured or partially curedcap layer disposed over the insert, the insert providing support to thepadding layer; c) positioning the insert in a mold; d) positioning thepadding layer in the mold proximate to the uncured or partially cureddisposed over the insert to form a sound insulating assembly; e) curingthe sound insulating assembly; f) removing the sound insulating assemblyfrom the mold; g) removing the insert from the assembly to form thesound insulating layered composite such that the sound insulatinglayered composite has a predetermined air flow resistance.
 17. Themethod of claim 16 wherein the air flow resistance is from about 300 toabout 6000 rayl.
 18. The method of claim 17 wherein the curable liquidcomposition comprises an acrylic latex, an ethylene vinyl acetate latex,a styrene butadiene rubber latex.
 19. A method of making a soundinsulating layered composite structure having a cap layer disposed overa padding layer, the method comprising: a) providing a padding layer,the padding layer having a preformed shaped; b) spraying a curableliquid composition onto a tool to form a uncured or partially cured caplayer; c) transferring the uncured or partially cured cap layer onto thepadding layer; and d) curing the uncured cap or partially cured caplayer to form the sound insulating composite layer such that the soundinsulating layered composite such that the sound insulating layeredcomposite has a predetermined air flow resistance.
 20. The method ofclaim 19 wherein the air flow resistance is from about 300 to about 6000rayl.